Process of making cellulose esters and the products resulting therefrom



f .Patented July 28, "1936' .PROCESS OF MAKING CELLULOSE ESTERS AND THEPRODUCTS RESULTING THERE:

, FROM Hans '1'. Clarke, New York, and Carl J. Malm, Rochester, N. Y.,assignors to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew York No Drawing. Application March 4, 1931, 1 Serial No. 520,149- I23 Claims. (01. 260-101 This invention relates to processes of makingorganic esters of cellulose in which the fatty acids of 3-4 carbon atomsor any mixture of these and a lower anhybrid are employed, preferably 5with the aid of a catalyst, and to products. resulting therefrom. Thelower anhydrids are also to be understood as including thoseanhydridswhich are derivatives of a fatty acid having less carbon atoms than theparticular fatty acid of 3-4 carbon atoms used, as well as theunsubstituted anhydrids. For. example, if propionic acid is emplqyed,some of the lower anhydrids which would be suitable to co-act therewithwould be acetic anhydrid, chloracetic anhydrid, or methoxy or '15 ethoxyacetic anhydrid.

This application is in part a continuation of our applications SerialNos. 179,176 and 179,177 filed March '28, 1927, now Patents Nos.1,800,860 and 1,880,808 respectively.

- One object of our inventionis to provide a process by which the simpleor mixed'esters of cellulose' containing propionyl and/or butyryl groupsare produced with theaid of the 'propionic or butyric acids without thenecessity of adding. the

anhydrids of these particular acids.

. Another object of our invention is to provide a process in'which thereis employed an organic acid anhydrid, which anhydrid impels the entranceof propionyl or butyryl groups into the cel- 3O lulose molecule. In oneform of our invention, the

, anhydrid iinpels esterification of the cellulose by the fatty acid oracids present in the esterifi tlon bath without itself contributing anyacyl groups to the ester. In another form" of our invention,

3 the anhydrid itself contributes acyl groupsas well as impels theentrance of higher acyl groups so that a mixed ester is formed.

Another object of our invention is to provide a process by which notonly easily esterified cellu- 0 losic bodies such as hydrocellulose,reverted cellulose, and cellulose ethers can be esterified, but by wh'chone can also esterify substantially undegraded cellulose such as cotton,surgical cotton wool, tissue paper from cotton stock and even sul- 45fite wood pulp, thereby producing cellulose esters of high quality or bywhich even chemically affected cellulose such as cellulose acetate,formate, nitrate orth'e like may be esterifie'd.

- Another object of our. invention is to provide 50 product which issuitable for making film, arti-- -1- -flcial' silk, sheeting and variousother articleswhich are now made of the nitrates or acetates ofcellulose. Our product is commercially use- --ful instead of. being achemical curiosity as'is taught in the prior art with reference to sometypes of cellulose acetate-propionates or butyrates.

Another object of our invention is to provide a product of improvedproperties (solubility, flexibility, strength, etc.) over theacetate-propionates or butyrates known priorto our invention. Ourproduct is especially valuable when colloidized as will be describedherein.

Another object of our invention is to provide an esterlfying process inwhich the ingredients of the esterifying bath are active and yet do notdegrade the cellulose or the esters produced at the temperatures used inthe process. Our process comprises the butyration or propionation (orboth) of cellulose or partly acylated cellulose by the use of butyric orpropionic acid and an anhydrid which impels the esterification. It ispreferred that asolvent of the resulting esters and a catalyst bepresent in the bath. Afterthe esterification has taken place the productis precipitated by adding the dope to a' precipitant such as water ormethyl alcohol, washe'd'and dried.

To convert the ester into a preferred form for' commerce, it may bedissolved in an organic solvent such as acetone orethylene chloride andthe solvent evaporated off, leaving the ester in colloidized form..

' Our process utilizes for .the impelling agent to cause theesterification of the cellulose by the propionic and butyrlc acids,either acetic anhydrid or its alkoxy or halogen substituted derivativesor if desired a mixture of acetic and alkoxy acetic anhydrids.v Thealkoxy acetic anhydrid preferredis the ethoxy substituted compoundalthough the methoxy substituted and'the higher alkoxy substitutedacetic anhydrids have been found suitable as well as the chloraceticanhydrids. a

-When butyi'ic acid is used for theesterification of the cellulose, theimpelling agent'may b ,pionic anhydrid, chlorpropionic anhydrid or analkoxy propionic anhydrid, instead of the acetic anhydride orits derivatves, if desired.

In carrying out our pro ess glacial acetic acid is usually employed asthe solvent-0f the acids, an

hydrids and the ester resulting from the reaction ethylene chloride mayalso be either added thereto or substituted Ior'the acetic acid. Alsothe propionic acid itself may be added'in sufiicientamounttoalsoactasthesolventinthereactionv mass although this wouldnot'be the mosteconomical. At the end of the esterificaiion, whensufiicient solvent is present, the organic ester or cellulose resultingi'romthe reaction is found to be in solution. 7

Although there are impurities in the technical anhydrids which exert acatalytic efi'ect on the reaction it is preferred that a catalyst,such-as sulfuric acid, perchlo'ric acid, um perchlorate, zinc chloride,para toluene sulio-chloride. benzene sulionic acid or the like which arecommonly employed i'or'acylation of cellulose, be

added to the mass.

Examples illustrative of our invention are as follows:

I..An esterii'ying bath is prepared comprising 20 parts by weightpropionic acid, 15 parts by a weight of acetic anhydrid and parts byweight of glacial acetic acid. There is also thoroughly incorporatedinto this bath one part by weight of fused zinc chloride as a catalyst.5 parts by weight of purified cotton-are thoroughly mixed into this bathand'the latter maintained at 60 to 65 C. until a clear mixtureor doperesults. This generally takes place in 35 hours or less. The resultingester is isolated by pouring into 'water,washingand dryinaasisc stem inmaking unmixed cellulose esters. The product contains not only acetylgroups but enough proandaclear pionyl, groups tomake the product solublein acetone, methyl acetate and in chloroform. It

- is also solublei'n ethyl acetate and ethylene chloride. The product iscellulose acetate propionate. is substantially fully esterified-andcontains 32% acetyl and propionyl.

lLAnestei-ii'yinghathisp mlpdcgnprising 75 pounds or butyrlc acid, 300pounds 01' acetic I anhydrid loo pounds-glacial acetic acid and- 1pound: magnesium perchlorate trihydrate 100 pounds of purified cottonare thoroughly mixed into this bath and the latter is maintained atBot-65'. C..1mtila clear mixture or dope results as above. Ai'terprecipitating, washing and drythe product is -iound to be soluble inacetone, ethyl acetate, ethylene chloride and chloroform. The product-iscellulose acetate butyrate, issubstantially fully esterified andcontains 31% 'acetyl and 18% butyry'tj 'm. An esteritying'bath is Ppared comprising 280 pounds propionic acid. It! poimds glacial tic acid,150' pounds acetic anhydrid (85%) and ti pound sulturic acid.(p. gr.1.85). 50

pounds'oi purified cotton are thoroughly mixed into thisbath and thelatter is allowed to rise from 60'400' 1". through 3s period oi. 5hours,

mixture or dope results. The prodf a t is precipitated, washed and driedand is found to be soluble in acetone, ethyl acetate, ethylene ing: 200

chloride and chlorotorm; 'Iheproduct is cellulose. acetate propionate',is substantially fully esterilfied and contains acetyl and 18% pro- IV.bath i's preparedcomprispounds 'propionic'zacid, v150 pounds aceticanhydrid (85%),150 pounds ethylenedichloride nd $6 pound sulfuric 'acid(spr; gr. 1.85). 50 fl unds of cotton are treated in this bath in themanner-disclosed in the preceding example. The

resulting -product is soluble in acetone,. ethyl acetate, ethylenechloride and chloroform. The

' substituted anhydrid as the impeller, one would iorm. F

- ing the propionic or butyric, acids individually,

will be produced. Alsocarrying out the process. Where butyric acid. isused. the im'pelling agent may be propionic i although other solventssuch, forlexample, as

and 17% propi nrl. v v Ourpr'ocessmavalsobcutiiiaedior producingthemiaedestersotcelluloseinfibrousiorm as shown.by thei'ollowingexample:

100 parts by weight or propionic acid containing- 1 part by weight oiperchloric acid are thor- 1 parts by weight of cotton I interval ofpretreatment.

From the above examples it 'will be observed that it is prei'errcd thatthe availableacyl radicals of atoms in the acylation bath 25 be atleastequal to and preferably in excess oi.'--

the available lower acyl radicals and that the higher acyl radicalsbes'upplied by the acid or acids of 3-4 carbon atoms and the lower acylesterifieation radicals by the lower acid anhydride. All of theavailable esterification radicals present in the esterification bathmust be taken into account. 01' course, should one employa.

have to have present in'the bath, at least two .Itisalsotobeunderstoodthatinstead ofustheacidsmaybemixe da-nd thus'acelluloseester containingboth propionyl and butyryl groups instead o!,using acetic. anhydridalone it may be mixed with a chloracetic anhydrid or an alkoxy aceticanhydrid in anhydrldor a mixture otv acetic and propionicanbydridsoreacliorbothoi'thesemayalsobe mixed with a chloracetic.oralkoxyacetic anhydrid. In fact" as -pure'propionic anhydrid moreexpensive than technical propionic anhyj vdri d which may containappreciable percentages oiacetic and butyric anhydrids, it-will beunderstood that both types oi propionic anhydrid are 65 referred toherein as propionic anhydrid.

We have found our cellulose acetate-propionatcs. acetate butyratu, andacetate-propi-.

onate-butyrates to be" soluble in ethylene chloride, acetone. ethylacetate and chloroform directly iron the reaction mass without anynecessity of hydrolyaing or deacylating. C'

The preparation oi compositions of matter, or articles therefrom, bydissolving the cellulose mixed organic esters or the cellulose higheres- 7 35" fatty acids of 2-4 carbon atoms in order to obten in ethylenechloride is not our joint invencontaining butyric acid and a lowerorganic acid tion but is the sole invention of Carl J. Malm, one oftheapplicants herein, as set forth in his application Serial No.551,545, filed July 17, 1931.

The mixed esters produced by our process, when colloidized such forexample, as by dissolving in acetone and then evaporating off thesolvent to form film, sheets, coatings, filaments, etc. are especiallyvaluable. Films, sheets and the like are formed by coating solutions ofthe ester upon wheels, fort instance, as shown in the Sulzer Patent No.1,466,733. Sheets so produced are very useful as photographic film basefor the reason that the sheets have the property of flatness (lyingfiat) to an unusual degree. Ordinary cellulose acetate sheets may beenhanced in flatness by coating them with solutions of ouracetatepropionate or by laminating them with thin sheets ofacetate-propionate or by mixing acetate-propionate with the acetatebefore coating;

Films, thin sheets (such as for wrappi g Durposes) artificial silkfilaments and the like produced from solutions of our celluloseacetate-propionate also are more water resistant than for instance,cellulose acetate products. Also due to this fact, thin sheeting ofcellulose acetate-propionate does not warp or wrinkle under humidconditions to the extent that some other sheetings do.

In producing artificial silk, a solution of the celluloseacetate-propionate in acetone, for instance, is extruded through fineorifices into a closed chamber through which passes a current of heatedair to coagulate the filament. The filament is then led out from thechamber to an outside wind up or cap spinning device, as known fordecades in the art. The thread may, of course, pass over lubricating,dyeing or other treating stations during its production.

Lacquers with highly useful properties may also be compounded in knownmanner from our cellulose aceto-propionates.

Other uses for our products as well as variations in their methods ofmanufacture may be suggested from time to time by those skilled in theart and the scope of our invention is to be determined only by theclaims appended here- What we claim as our invention and desire tosecure by Letters patent of the United States is: l. A process of makinga mixed organic acid ester of cellulose-which comprises acylatingcellulose or a cellulose compound containing esterifiable hydroxylgroups with a reaction mixture containing a fatty acid of 3-4 carbonatoms, a

lower organic acid anhydride, and glacial acetic acid. I

2. A process of making a cellulose ester which comprises acylatingcellulose or a cellulose com- 4. A process of making a mixed organic133m ester of cellulose which campin acylating cellulose or a cellulosecompound containing esterifiable hydroxyl groups with a reaction mixtureI of cellulose which comprises acylating cellulose or a cellulosecompound containing esteriflable hy-,

anhydride.

5. Aprocess of making a mixed organic acid ester droxyl groups with areaction mixture containing propionic acid and a lower organic acidanhydride.

6. A process of making a mixed organic acid ester of cellulose whichcomprises acylating cel- I lulose or a cellulose compound containingesteriflable hydroxyl groups with a reaction mixture containing a fattyacid of 3-4 carbon atoms and acetic anhydride.

7. A process of making a mixed organic acid ester of cellulose whichcomprises acylating cellulose or a cellulose compound containingesterifiable hydroxyl groups with a reaction mixture containing butyricacid and acetic anhydride.

8. A process of making a mixed'organic acid 20 ester of cellulose whichcomprises acylating cellulose or a cellulose compound containingesterifiable hydroxyl groups with a reaction mixture containingpropionic acid and acetic anhydride.

9. A process of making a mixed organic acid ester .of cellulose whichcomprises acylating cellulose or a cellulose compound containingesterifiable hydroxyl groups with a reaction mixture containing a fattyacid of 3-4 carbon atoms, a lower organic acid anhydride and a commonsolven 10. A process of making a mixed organic acid ester of cellulosewhich comprises esterifying cellulose with a. reaction mixturecontaining a fatty acid of three to four carbon atoms anda lower organicacid anhydride.

11. A process of making a mixed organic acid ester of cellulose whichcomprises esterifying cellulose with a reaction mixture containingbutyric acid and acetic anhydride.

12. A process of making a mixed organic acid ester of cellulose whichcomprises esterifying cellulose with a reaction mixture containingpropionic acid and acetic anhydride.

13. A process of making a mixed organic acid ester of cellulose whichcomprises treating cellulose or a cellulose compound containingesterifiable hydroxyl groups with a reaction mixture containing a fattyacid of 3-4 carbon atoms, a lower organic acid anhydride and a catalyst.

14. A process of making a mixed organic acid ester of cellulose whichcomprises acylating cellulose or a cellulose compound containingesterifiable hydroxyl groups with a reaction mixture containingpropionic and butyric acids and a lower organic .acid anhydride.

17. A process of making a mixed organic acid ester of cellulose whichcomprises acylating cellulose or a cellulose compound containingesterifiable hydroxyl groups with a reaction mixture containing butyricacid and-propionic anhydride. 18. A mixed organic acid ester ofcellulose resulting from the acylatingofheellulose or a 0421- lulosecompound containing etteriflable hydroxyl 7 groups with propion'ic andbutyric acids and a lower organic acid anhydride.

19. A mixed organic acid ester of cellulose resulting from the acylatingof a celluloslc material with butyric and proplonic acids and acetican-' I ganic acid ester of cellulose containing afatty acid radical of3-4 carbon atoms and a lower fatty acidradical of more than one carbonatom.

21, Substantially fully esterified cellulose acetate propionate. v

22. Substantially fully esterified cellulose acetate butyrate.

23. Substantially fully esterlfled cellulose acetatepropionate-butyrate.'

HANS T. CLARKE. CARL J. MALM.

